Signal digitizer-finder system prototype for TA fluorescence telescope

The Telescope Array (TA) experiment plans to deploy an array of 3 fluorescence telescope stations and scintillation counter array in the west desert of Utah, and observes extremely high energy cosmic rays by the atmospheric fluorescence and air shower particles. In order to identify the origin of super-GZK (E>10²⁰ eV) events, TA has ∼30 times larger aperture than AGASA and provides a particle identification by the shower profile measurement. Each fluorescence detector (FD) station includes 12 telescopes, and each telescope detects fluorescence light with 16×16 photomultipliers. The PMT signal caused by fluorescence is led to VME modules after amplification by the preamplifier that was united to PMT. The first module called signal digitizer-finder (SDF) bears a role of finding a first level trigger. This first level trigger is sent to track finder (TF) module, and the TF decides whether the signal is due to the air shower by finding a ´track´. When the air shower track is found the TF sends the second level trigger to a central trigger distributor (CTD) module. The CTD collects 2nd level trigger from any TF module and distributes the information to others. Now, we started to manufacture such electronics somewhat later than the construction of the FD station and the telescopes.